In treatment of brain swelling, cerebral perfusion pressure (CPP) is a critical parameter defined as the difference between mean arterial blood pressure and intracranial pressure (ICP). While mean arterial blood pressure can be routinely monitored, a safe, accurate, inexpensive, reliable, small, implantable pressure telemetry unit is needed to routinely monitor ICP. An integrated circuit, chronically implantable temperature and pressure telemetry unit that will satisfy these criteria is proposed. Power and data telemetry will be mounted on a subcutaneous cranial bolt with a pressure sensor mounted on the bottom or on an intraparenchymal probe. Following in-vitro testing, epidural, subdural and intraparenchymal sensors will be implanted in four animals. Telemetered outputs will be compared with standard readings for 3 months to assess stability and accuracy in mammalian brain. Potential candidates for telemetered ICP include patients with head trauma, brain tumor, pseudotumor cerebri, intracerebral and subarachnoid hemorrhage, hydrocephalus, neurosurgical postop brain swelling, Reye's syndrome, brain infections and toxic/metabolic encephalopathies. Outpatient uses may include detection of brain swelling in patients undergoing radiation therapy for tumors, or recovering from head trauma and monitoring hydrocephalus. Phase II will focus on longer term testing, manufacturing issues, clinical trials, and incorporation of additional sensing modalities. PROPOSED COMMERCIAL APPLICATIONS: If successful, the proposed telemeters will provide a safe, accurate, inexpensive, reliable, small device for readout of intracranial pressure and temperature. It will be marketed for emergency and intensive care monitoring of intracranial pressure in cases of head trauma and many other conditions. The telemeters may also be marketed as a chronically implantable device for home monitoring for hydrocephalus or other chronic conditions that may result in excessive intracranial pressure.